The Electronic Structure and the Nature of Chemical Bond of Crystalline Li12Si7. A Semiempirical Crystal Orbital (CO) Approach Based on the Self‐Consistent‐Field (SCF) Approximation in the Hartree‐Fock (HF) Scheme Applied to One‐Dimensional (1D) Subunits of the Li12Si7 Solid

Abstract

AbstractThe electronic structure of crystalline Li12Si7 has been studied by means of crystal orbital (CO) calculations based on the tight‐binding formalism. The computational basis for this investigation is a semiempirical INDO model derived in the framework of the SCF HF approximation. The Li12Si7 system is divided into two substructures containing one‐dimensional infinite columns Li6Si5 and Li12Si4, respectively, which are employed as stacking units in the tight‐binding calculations. The band structure properties, density of states profiles, charge distributions and the nature of the various diatomic interactions for both substructures are discussed. In order to understand the nature of Si‐Si, Li‐Si and Li‐Li interactions we have decomposed the various diatomic potentials into elements of physical significance, i.e. covalent resonance energies, exchange parameters as well as electrostatic potentials. The one‐dimensionality of the Li6Si5 unit is partially the result of covalent Li‐Si interactions in the direction of the stacking axis. The nature and strength of the Li‐Si coupling depends strongly on the conformation of the 1D arrangement. The electronic structure (i.e. localization properties of the CO microstates) in the second fragment Li12Si4 differs drastically from the one‐electron properties encountered in the Li6Si5 system. The identity of the orbitals of the twelve Li and four Si atoms is significantly perturbed in the 1D fragments, CO microstates are predicted that contain nearly comparable admixtures from the Si and Li sites.